From Blasters to Phasers: How Close Are We to Laser Guns?

From Blasters to Phasers: How Close Are We to Laser Guns?

Everyone loves the idea of laser guns. But are their fictional depictions realistic, and how close are we to creating actual, handheld energy weapons?

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Pffft. Lasers are so yesterday. Everyone knows railguns are the future now.

Weirdly enough, this came up while I was in discussion with a friend who wanted to know the technical end of projectile versus "beam" weapons, so the formula from one of the middle pages had flashed through my head a couple times just recently.

You can't just multiply mass and velocity together to get momentum when you're dealing with objects moving near the speed. That figure you quoted for a neutron travelling at c is more like the momentum of a neutron travelling at about 0.7c

Also, I'm gonna need serious citations for your claim that electromagnetic fields do not conserve momentum. Conservation laws arise from symmetries, by Noether's theorem. Are you telling me that the laws of physics change depending on where you are?

EDIT: Ah, I notice the disclaimer that you are not accounting for special relativity. Still, it seems odd to try to predict the properties of objects moving near c without using the theory that tells you about the properties of objects moving near c.

I can't imagine the Heat Ray as a non-lethal weapon with pain in under five seconds.

Honestly that sounds like a nightmarish, devil weapon.

Non-lethal frying people alive with microwaves.

Redingold:
You can't just multiply mass and velocity together to get momentum when you're dealing with objects moving near the speed. That figure you quoted for a neutron travelling at c is more like the momentum of a neutron travelling at about 0.7c

In my early calculations, I used the equation for relativistic momentum.
(Source: http://en.wikipedia.org/wiki/Momentum#Relativistic_mechanics)

The resulting momentum was somewhere around to the power of -12; the problem is that the number varies widely depending on what you plug in for velocity. It added multiple layers of additional complication to the article that would have been lost on most readers, all to make the same basic point. Also, from my research, it seems even physicists don't all agree on how special relativity applies to momentum.

Redingold:
Also, I'm gonna need serious citations for your claim that electromagnetic fields do not conserve momentum. Conservation laws arise from symmetries, by Noether's theorem. Are you telling me that the laws of physics change depending on where you are?

It's not that they don't conserve momentum, it's that, "electromagnetic fields violate Newton's law of action and reaction and do not conventionally follow the principles of conservation of momentum."

(Source: http://en.wikipedia.org/wiki/Momentum#Classical_electromagnetism)

Again, it simply adds additional layers of complication. To thoroughly address the physics of the recoil problem would require an entire article in and of itself, and it would only be interesting to a very small audience.

That said, if you would like to run any calculations, I'd be happy to update the article, and I absolutely encourage any and all thought-provoking discussion that either corroborates or challenges what I have written :)

Particle beam weapons don't rely on "punch", the beam splits matter apart at the sub-atomic level. The mass of the target is directly related to the damage caused; More mass, more damage.

UsefulPlayer 1:
I can't imagine the Heat Ray as a non-lethal weapon with pain in under five seconds.

Honestly that sounds like a nightmarish, devil weapon.

Non-lethal frying people alive with microwaves.

http://en.wikipedia.org/wiki/Active_Denial_System#Effects

You don't need to heat anything other than the surface to cause pain since the nerve endings are all near the surface of the skin. It is a pretty nightmarish weapon in concept, beaming pain onto a person's skin is not something I find that good, However it can be blocked by tinfoil (Free your miiiiind) and other metals like any other microwave. Oh and it's less harmful to people it hits than bullets or beanbags (bruising and tissue injuries... oh and shattering bones like ribs which has caused bone shards to pierce hearts.) or even water cannon or tear gas. (Cases of blinding and damage to eyes and bones in the face and killing people who have asthma or chemical burns or in cases of close exposure to the eyes, chemical inflammation on the eyes causing permanent eyesight damage).

When weighed up against the other main riot control weapons this heat ray thing is much, much safer...

People never consider finances when dreaming of the future.

Why don't we have flying cars? It's not financially feasible.
Why don't we have cybernetic implants/prosthetics (and never will, for the masses)? See above.
Why don't we have guns that shoot laser beams....

Why don't we have spaceships that anyone can hop in to colonize a planet of their choice? Finances!

This post is more humorous if you imagine me pronouncing finances wrong and with a funny voice.

michael87cn:
People never consider finances when dreaming of the future.

Why don't we have flying cars? It's not financially feasible.
Why don't we have cybernetic implants/prosthetics (and never will, for the masses)? See above.
Why don't we have guns that shoot laser beams....

Why don't we have spaceships that anyone can hop in to colonize a planet of their choice? Finances!

This post is more humorous if you imagine me pronouncing finances wrong and with a funny voice.

Hahah, great point! And I definitely agree with regards to flying cars, cybernetic prosthetics and spaceships, but the one thing that humanity has proven it will spare no dime on is military. (Or, at least certain governments...) Billions of dollars have gone into simple R&D for these technologies, let alone their actual battlefield implementation.

Rhykker:

Redingold:
You can't just multiply mass and velocity together to get momentum when you're dealing with objects moving near the speed. That figure you quoted for a neutron travelling at c is more like the momentum of a neutron travelling at about 0.7c

In my early calculations, I used the equation for relativistic momentum.
(Source: http://en.wikipedia.org/wiki/Momentum#Relativistic_mechanics)

The resulting momentum was somewhere around to the power of -12; the problem is that the number varies widely depending on what you plug in for velocity. It added multiple layers of additional complication to the article that would have been lost on most readers, all to make the same basic point. Also, from my research, it seems even physicists don't all agree on how special relativity applies to momentum.

Redingold:
Also, I'm gonna need serious citations for your claim that electromagnetic fields do not conserve momentum. Conservation laws arise from symmetries, by Noether's theorem. Are you telling me that the laws of physics change depending on where you are?

It's not that they don't conserve momentum, it's that, "electromagnetic fields violate Newton's law of action and reaction and do not conventionally follow the principles of conservation of momentum."

(Source: http://en.wikipedia.org/wiki/Momentum#Classical_electromagnetism)

Again, it simply adds additional layers of complication. To thoroughly address the physics of the recoil problem would require an entire article in and of itself, and it would only be interesting to a very small audience.

That said, if you would like to run any calculations, I'd be happy to update the article, and I absolutely encourage any and all thought-provoking discussion that either corroborates or challenges what I have written :)

Ah, I see the problem. The statement on Wikipedia is somewhat misleading. It's true that the Biot-Savart law predicts that two moving charged particles don't necessarily exert equal and opposite forces on one another, but this is a case of misapplying the Biot-Savart law, which only holds in magnetostatic cases. Two moving charges can not be treated as such a case, only constant currents can be considered in such cases. If steady currents are considered, the Biot-Savart law is consistent with Newton's third law.

I'm not massively clued up on my classical electromagnetism, and the calculus is beyond the scope of this comment (also I'm not fiddling around with LaTeX at three in the morning to make my integrals look nice) so I'll refer you to this: http://iweb.tntech.edu/murdock/ph4610/MagForcesN3.pdf

michael87cn:
Why don't we have flying cars? It's not financially feasible.
Why don't we have cybernetic implants/prosthetics (and never will, for the masses)? See above.
Why don't we have guns that shoot laser beams....

Why don't we have spaceships that anyone can hop in to colonize a planet of their choice? Finances!

And what's funny is that you are dead wrong on all of these.
A) No flying cars because the materials science currently does not allow for compact VTOL with any appreciable range, and even if it did the insurance for such a vehicle would bankrupt someone, let alone the cost of the vehicle itself.
B) Over the past 15 years cybernetic prostheses have advanced TREMENDOUSLY. Within another 15-30, who knows.
C) You could easily build a gun that fires laser beams. Of course, anyone whose seen Real Genius knows that the only way to make lasers which don't require insane amounts of energy ends up venting extremely toxic and hot chemical byproducts. So either it would be banned under NBC treaties, or it would require you to cart around a car sized cart of batteries and capacitors.

D) Sorry, but the materials science just isn't there for a solar sail/ion engine slowship, there isn't enough interstellar matter for a Bussard design to work, and even assuming we could generate the energy for an Alcubierre warp drive, unless you could genereate a double bubble, everybody inside it would die from the Hawking radiation once it broke lightspeed. I suppose you could theoretically convert a large enough asteroid as a slowship and use an Orion drive to kick it extrasolar. Of course, steering it might be a bit difficult.

Oh hey, what's this? A 6kW pulse rifle? For sale? Right now?

http://www.amazing1.com/products/laser-ray-gun-assembled-kit-or-plans.html

moosemaimer:
Oh hey, what's this? A 6kW pulse rifle? For sale? Right now?

http://www.amazing1.com/products/laser-ray-gun-assembled-kit-or-plans.html

Maybe if you pointed it at somebody's eye. Or you just wanted to pop a balloon or vapourize a tiny amount of something.

Calling a "pulse rifle" is a bit ridiculous.

Any energy source compact enough to be portable and energetic enough be able to power a lethal laser would be more militarily effective as an explosive.

Rhykker:
It's not that they don't conserve momentum, it's that, "electromagnetic fields violate Newton's law of action and reaction and do not conventionally follow the principles of conservation of momentum."

(Source: http://en.wikipedia.org/wiki/Momentum#Classical_electromagnetism)

Again, it simply adds additional layers of complication. To thoroughly address the physics of the recoil problem would require an entire article in and of itself, and it would only be interesting to a very small audience.

As Redingold points out, this is still not actually correct. Electromagnetic fields absolutely do follow conservation of momentum. Sure, the maths is a little more complicated that classical physics, but if you're trying not to confuse your readers stating something that is so misleading is hardly going to help matters. Why not just say "they do obey conservation of momentum, but the exact details are too complex to get into here" or something?

Also, from my research, it seems even physicists don't all agree on how special relativity applies to momentum.

Your research is wrong. Special relativity is first year undergrad stuff, and is extremely well understood and thoroughly tested. If we didn't agree on how it worked, building particle accelerators would be simply impossible. As an accelerator physicist, that would make my job a little tricky.

Rhykker:
At this point, it's just a matter of engineering and advances in miniaturization. If it seems hard to believe we'll ever get laser weapons down to handheld size, just remember that the first computer weighed more than 60,000 lb, measured roughly 8 by 3 by 100 feet, and consumed 150 kW of power.

This again just doesn't make sense. We could miniaturise computers because they don't actually need to use 150kW, that was the result of inefficiencies in the design. With a kW or MW class laser, that power is the entire point of the thing. It doesn't matter how small you can make things or how advanced your technology might be, if you want to have a MW of power hitting something, your laser needs to be provided with at least a MW of power. A handheld laser won't help much if you still need to tow a power station along with it.

It also seems rather odd that you didn't mention things like THEL and Iron Beam. The YAL-1 you did mention is so large because it's intended to shoot down large ballistic missiles from hundreds of kilometres away. Systems like THEL, on the other hand, have already been demonstrated to be capable of taking out incoming artillery and mortar shells, as well as UAVs, and similar systems could be in active service within a couple of years. For an article about whether we could have actual working laser guns, not including examples of the actual working laser guns we already have seems a bit of an odd choice.

Kahani:
It also seems rather odd that you didn't mention things like THEL and Iron Beam. The YAL-1 you did mention is so large because it's intended to shoot down large ballistic missiles from hundreds of kilometres away. Systems like THEL, on the other hand, have already been demonstrated to be capable of taking out incoming artillery and mortar shells, as well as UAVs, and similar systems could be in active service within a couple of years. For an article about whether we could have actual working laser guns, not including examples of the actual working laser guns we already have seems a bit of an odd choice.

The focus of the article is on handheld laser guns for antipersonnel use; YAL-1 was mentioned only in passing because of this. I would classify these things more as defense systems than as laser guns. We have a number of laser technologies for knocking out incoming missiles -- they either require focusing the beam on a specific point of the target for several seconds, which works great for a projectile with a calculable trajectory but sucks against a human, or they don't cause direct damage to a warhead but rather heat up its ignition system.

Rhykker:
The focus of the article is on handheld laser guns for antipersonnel use; YAL-1 was mentioned only in passing because of this. I would classify these things more as defense systems than as laser guns.

But that's a meaningless distinction, it's simply a matter of scale. And given that scale and miniaturisation was exactly the point I was responding to, failing to note how much we've already done on that front seems quite an odd omission.

We have a number of laser technologies for knocking out incoming missiles -- they either require focusing the beam on a specific point of the target for several seconds, which works great for a projectile with a calculable trajectory but sucks against a human

Nonsense. They require focussing on a target for several seconds because missiles and the like are large lumps of metal that takes time to burn through, and even then simply making a hole won't achieve much unless it's in the right place. You could easily burn through a squishy human with the same system in no time at all. The reason they're not used against people is simply that there are many cheaper ways of killing humans precisely because they're so squishy, as well as generally a lot slower.

 

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